1. Field of the Invention
The invention relates to Ethernet, and more particularly to 1000 BASE-T Ethernet signals.
2. Description of the Related Art
1000 BASE-T is one implementation of Gigabit Ethernet, a computer network that transmits data at a nominal speed of 1 gigabit per second. It can use Cat (Category) 5 cable, Cat 5e (Category 5 enhanced) cable, and Cat 6 cable. The cable contains four twisted copper wire pairs, through all of which the Gigabit Ethernet physical layer signals are simultaneously transmitted.
Because the Ethernet physical layer (PHY) signals transmitted through four duplex channels may suffer from different delays, Ethernet PHY signals transmitted at one time may be received by a receiver at different times, an effect known as “signal skew” or “signal misalignment”. According to the IEEE 802.3ab standard for Gigabit Ethernet, there may be no more than 50 ns signal skew between the Ethernet PHY signals transmitted on the four duplex channels, or the signal misalignment between the four duplex channels may be at most 7 symbols. The signal skew, however, must be eliminated before the Ethernet PHY signals are decoded by a Viterbi decoder, which only decodes contemporary signal symbols. A method for deskewing Ethernet physical layer signals is therefore required.